BE/CNH: Coupling Human and Natural Influences on Coastline Evolution as Climate Changes

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Sandy coastlines such as the U.S. Southeast and Gulf coasts are constantly shifted and reshaped as breaking waves move sand from one location to another. Research into how such coastlines evolve over spatial scales of kilometers to hundreds of kilometers and over time scales of decades and longer has just begun. Recent work has revealed surprising long-range interactions, with changes in one location directly affecting distant parts of the coastline. Human efforts to stabilize the shoreline position -- especially through artificial sand placement or "beach nourishment" -- are becoming increasingly prevalent, and these localized manipulations likely affect how entire coastlines evolve through their long-range as well as regional effects. This research project will incorporate human manipulations into an enhanced computer model of large-scale, long-term coastline change caused by wave-driven sediment transport. Addressing the behaviors of the fully coupled human-natural system will require developing a model that represents how humans respond to coastline changes, especially local shoreline erosion. Such a model will be based on (1) data that incorporates historical beach-nourishment decisions and economic variables; (2) economic theory;( 3) information gathered during a workshop involving coastal managers, engineers, policy makers, and stakeholders; and (4) scenarios of federal beach-nourishment subsidies, future expense of procuring beach-quality sand, and policy constraints arising from ecological concerns. The resulting coupled model will allow investigations of the types of coastline behaviors to be expected in coming decades and centuries in the context of likely climate change and the consequent changes in storm and wave patterns as well as accelerated sea-level-rise. The coastline of the Carolinas will be used as an initial case study to test the model.Developing the social science component of the modeling endeavor will involve the first examination of how beach nourishment decisions are made. Experiments using the coupled human-coastline model will provide the first examination of how human-influenced coastlines evolve, and more specifically, how actions taken at one location are likely to affect other coastal communities in far-flung locations as well as nearby. The potential insights gained through this work could help coastal managers and planners avoid surprises arising from such spillover effects, which could be especially important as climate change and direct human manipulations become more important factors affecting coastline change. A dedicated website and targeted communications will facilitate dissemination of the main lessons to interested coastal planners and stakeholders. More broadly, this research will advance the embryonic science of human-landscape interactions, which are becoming ubiquitous across much of the Earth's surface. This project is supported by an award resulting from the FY 2005 special competition in Biocomplexity in the Environment focusing on the Dynamics of Coupled Natural and Human Systems.